which did not match to his desired result. So I skipped the first LAG (on C1) in anticipatory obedience.

But while playing around with his example I figured that it felt strange to have in C1 always the same redundant data. That's why I suspected, that he just wants to subtract the previous C2 from a given / inital value (which he repeats in C1 over and over again). That's why I came up with the second solution which might a little bit over shot .

In the end he seems to be happy with what he's got.

Anyway. Thanks again for your correction. I'll incorporate that knowledge in future solutions